U.S. patent application number 10/500576 was filed with the patent office on 2005-06-02 for electrolytic processing apparatus and method.
Invention is credited to Kobata, Itsuki, Kumekawa, Masayuki, Mori, Yuzo, Shirakashi, Mitsuhiko, Toma, Yasushi, Yasuda, Hozumi.
Application Number | 20050115838 10/500576 |
Document ID | / |
Family ID | 19190647 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050115838 |
Kind Code |
A1 |
Mori, Yuzo ; et al. |
June 2, 2005 |
Electrolytic processing apparatus and method
Abstract
There is provided an electrolytic processing apparatus and
method that can effect processing of a substrate with high
processing precision and can produce an intended form of processed
substrate with high accuracy of form. The electrolytic processing
apparatus includes: a holder (30) for holding a substrate (W); a
processing electrode (32) that can come close to the substrate; a
feeding electrode (34) for feeding electricity to the substrate; an
ion exchanger (40) disposed in the space between the substrate and
the processing electrode, or the substrate and the feeding
electrode; a fluid supply section (70) for supplying a fluid into
the space; a power source (68) for applying a voltage between the
processing electrode and the feeding electrode; a drive sections
(44, 56 and 60) for allowing the substrate and the processing
electrode, facing each other, to make a relative movement; and a
numerical controller (72) for effecting a numerical control of the
drive sections. ATTACHMENT "B"
Inventors: |
Mori, Yuzo; (Osaka, JP)
; Shirakashi, Mitsuhiko; (Tokyo, JP) ; Kumekawa,
Masayuki; (Tokyo, JP) ; Yasuda, Hozumi;
(Tokyo, JP) ; Kobata, Itsuki; (Tokyo, JP) ;
Toma, Yasushi; (Kanagawa, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
19190647 |
Appl. No.: |
10/500576 |
Filed: |
January 4, 2005 |
PCT Filed: |
January 7, 2003 |
PCT NO: |
PCT/JP03/00038 |
Current U.S.
Class: |
205/81 ;
204/229.4 |
Current CPC
Class: |
B23H 3/00 20130101; C25F
7/00 20130101; B23H 5/08 20130101; B23H 3/08 20130101; C25F 3/00
20130101 |
Class at
Publication: |
205/081 ;
204/229.4 |
International
Class: |
C25B 009/04; C25D
021/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 8, 2002 |
JP |
2002-1737 |
Claims
1. An electrolytic processing apparatus, comprising: a holder for
detachably holding a workpiece; a processing electrode that can
come close to or into contact with the workpiece held by the
holder; a feeding electrode for feeding electricity to the
workpiece held by the holder; an ion exchanger disposed in at least
one of the space between the workpiece and the processing electrode
and the space between the workpiece and the feeding electrode; a
fluid supply section for supplying a fluid between the workpiece
and at least one of the processing electrode and the feeding
electrode, in which the ion exchanger is present; a power source
for applying a voltage between the processing electrode and the
feeding electrode; a drive section for allowing the workpiece held
by the holder and the processing electrode, facing each other, to
make a relative movement; and a numerical controller for effecting
a numerical control of the drive section.
2. The electrolytic processing apparatus according to claim 1,
wherein the power source supplies an electric current or a voltage
controlled at a constant value between the processing electrode and
the feeding electrode.
3. The electrolytic processing apparatus according to claim 2,
wherein the numerical controller numerically controls the relative
movement speed between the workpiece held by the holder and the
processing electrode via the drive section.
4. The electrolytic processing apparatus according to claim 2,
wherein the numerical controller numerically controls a stop time
in a relative step movement of the workpiece held by the holder and
the processing electrode via the drive section.
5. An electrolytic processing method, comprising: providing a
processing electrode, a feeding electrode and an ion exchanger
disposed in at least one of the space between a workpiece held by a
holder and the processing electrode and the space between the
workpiece and the feeding electrode; allowing the processing
electrode to be close to or in contact with the workpiece held by
the holder while feeding electricity from the feeding electrode to
the workpiece; supplying a fluid to the space between the workpiece
and at least one of the processing electrode and the feeding
electrode, in which the ion exchanger is present; applying a
voltage between the processing electrode and the feeding electrode;
and allowing the workpiece held by the holder and the processing
electrode, facing each other, to make a relative movement while
numerically controlling the movement by a numerical controller.
6. The electrolytic processing method according to claim 5, wherein
an electric current or a voltage controlled at a constant value is
supplied between the processing electrode and the feeding
electrode.
7. The electrolytic processing method according to claim 6,
comprising: measuring the form of the workpiece before and/or
during processing; inputting coordinate data on the measured form
and on an intended form after processing of the workpiece to the
numerical controller; and numerically controlling the relative
movement speed between the workpiece held by the holder and the
processing electrode according to the coordinate difference between
the measured form and the intended form.
8. The electrolytic processing method according to claim 6,
comprising: measuring the form of the workpiece before and/or
during processing; inputting coordinate data on the measured form
and on an intended form after processing of the workpiece to the
numerical controller; and numerically controlling a stop time in a
relative step movement of the workpiece held by the holder and the
processing electrode according to the coordinate difference between
the measured form and the intended form.
Description
TECHNICAL FIELD
[0001] This invention relates to an electrolytic processing
apparatus and method, and more particularly to an electrolytic
processing apparatus and method useful for processing a conductive
material present in the surface of a substrate, such as a
semiconductor wafer, or for removing impurities adhering to the
surface of a substrate.
BACKGROUND ART
[0002] In recent years, instead of using aluminum or aluminum
alloys as a material for forming interconnection circuits on a
substrate such as a semiconductor wafer, there is an eminent
movement towards using copper (Cu) which has a low electric
resistivity and high electromigration resistance. Copper
interconnects are generally formed by filling copper into fine
recesses formed in the surface of a substrate. There are known
various techniques for forming such copper interconnects, including
CVD, sputtering, and plating. According to any such technique, a
copper film is formed in the substantially entire surface of a
substrate, followed by removal of unnecessary copper by chemical
mechanical polishing (CMP).
[0003] FIGS. 8A through 8C illustrate, in sequence of process
steps, an example of forming such a substrate W having copper
interconnects. As shown in FIG. 8A, an insulating film 2, such as
an oxide film of SiO.sub.2 or a film of low-k material, is
deposited on a conductive layer 1a in which semiconductor devices
are formed, which is formed on a semiconductor base 1. A contact
hole 3 and a trench 4 for interconnects are formed in the
insulating film 2 by the lithography/etching technique. Thereafter,
a barrier layer 5 of TaN or the like is formed on the entire
surface, and a seed layer 7 as an electric supply layer for
electroplating is formed on the barrier layer 5.
[0004] Then, as shown in FIG. 8B, copperplating is performed on to
the surface of the substrate W to fill the contact hole 3 and the
trench 4 with copper and, at the same time, deposit a copper film 6
on the insulating film 2. Thereafter, the copper film 6 and the
barrier layer 5 on the insulating film 2 are removed by chemical
mechanical polishing (CMP) so as to make the surface of the copper
film 6 filled in the contact hole 3 and the trench 4 for
interconnects and the surface of the insulating film 2 lie
substantially on the same plane. An interconnection composed of the
copper film 6 as shown in FIG. 8C is thus formed.
[0005] Components in various types of equipments have recently
become finer and have required higher accuracy. As sub-micro
manufacturing technology has commonly been used, the properties of
materials are largely influenced by the processing method. Under
these circumstances, in such a conventional machining method that a
desired portion in a workpiece is physically destroyed and removed
from the surface thereof by a tool, a large number of defects may
be produced to deteriorate the properties of the workpiece.
Therefore, it becomes important to perform processing without
deteriorating the properties of the materials.
[0006] Some processing methods, such as chemical polishing,
electrolytic processing, and electrolytic polishing, have been
developed in order to solve this problem. In contrast with the
conventional physical processing, these methods perform removal
processing or the like through chemical dissolution reaction.
Therefore, these methods do not suffer from defects, such as
formation of an altered layer and dislocation, due to plastic
deformation, so that processing can be performed without
deteriorating the properties of the materials.
[0007] A processing method, which makes use of a catalytic reaction
of the ion exchanger and carries out processing in ultrapure water,
has been developed as electrolytic processing. FIG. 9 illustrates
the principle of this electrolytic processing. FIG. 9 shows the
ionic state when an ion exchanger 12a mounted on a processing
electrode 14 and an ion exchanger 12b mounted on a feeding
electrode 16 are brought into contact with or close to a surface of
a workpiece 10, while a voltage is applied via a power source 17
between the processing electrode 14 and the feeding electrode 16,
and a liquid 18, e.g. ultrapure water, is supplied from a liquid
supply section 19 between the processing electrode 14, the feeding
electrode 16 and the workpiece 10. In the case of this electrolytic
processing, water molecules 20 in the liquid 18 such as ultrapure
water are dissociated efficiently by using the ion exchangers 12a,
12b into hydroxide ions 22 and hydrogen ions 24. The hydroxide ions
22 thus produced, for example, are carried, by the electric field
between the workpiece 10 and the processing electrode 14 and by the
flow of the liquid 18, to the surface of the workpiece 10 opposite
to the processing electrode 14 whereby the density of the hydroxide
ions 22 in the vicinity of the workpiece 10 is enhanced, and the
hydroxide ions 22 are reacted with the atoms 10a of the workpiece
10. The reaction product 26 produced by this reaction is dissolved
in the liquid 18, and removed from the workpiece 10 by the flow of
the liquid 18 along the surface of the workpiece 10. Removal
processing of the surface of the workpiece 10 is thus effected.
[0008] With the electrolytic processing of an electrically
conductive material carried out by using an ion exchanger in the
above-described manner, it is not possible to directly apply
thereto a numerical control mechanism generally employed in
conventional mechanical processing. In this regard, an electrolytic
processing method utilizes a chemical interaction between OH.sup.-
ions and the atoms of a workpiece. Accordingly, the processing
phenomenon occurs even when a workpiece and a tool (electrode) is
not in contact with each other. Electrolytic processing is thus
differentiated in the processing principle from mechanical
processing in which processing is effected by physical destruction
of a workpiece. More specifically, in a common mechanical
processing, processing is effected by allowing a workpiece and a
tool, which are in contact with each other, to make a relative
movement so as to physically destruct the workpiece. The progress
of processing may be stopped by releasing the contact between the
workpiece and the tool e.g. when a processing amount is reached to
an intended processing amount The processing does not progress any
more even when the tool passes over the surface of the workpiece.
On the other, according to the electrolytic processing method which
utilizes a chemical interaction between the reaction species and a
workpiece, as described above, the processing phenomenon occurs
when the amount of the reaction species reaches a certain level,
even when the tool (electrode) is not in contact with the
workpiece. Accordingly, the processing phenomenon inevitably occurs
when the tool (electrode) passes over the surface of a portion of
the workpiece in which a predetermined amount of processing has
been effected.
[0009] Accordingly, in order to perform processing of an
electrically conductive material with a high processing precision
that follows an intended form of a processed workpiece, by the
electrolytic processing method utilizing the chemical interaction
between the reaction species and the workpiece, such a control
system is needed that does not simply control the contact state
(position of tool) between the workpiece and the tool as is the
case of mechanical processing, but also control the chemical
interaction between the reaction species, such as OH.sup.- ions,
and the atoms of the workpiece.
DISCLOSURE OF INVENTION
[0010] The present invention has been made in view of the above
situation in the background art. It is therefore an object of the
present invention to provide an electrolytic processing apparatus
and method that can effect processing of a workpiece, having in the
surface an electrically conductive material as a to-be-processed
material, with high processing precision and can produce an
intended form of processed workpiece with high accuracy of
form.
[0011] In order to achieve the above object, the present invention
provides an electrolytic processing apparatus, comprising: a holder
for detachably holding a workpiece; a processing electrode that can
come close to or into contact with the workpiece held by the
holder; a feeding electrode for feeding electricity to the
workpiece held by the holder; an ion exchanger disposed in at least
one of the space between the workpiece and the processing electrode
and the space between the workpiece and the feeding electrode; a
fluid supply section for supplying a fluid between the workpiece
and at least one of the processing electrode and the feeding
electrode, in which the ion exchanger is present; a power source
for applying a voltage between the processing electrode and the
feeding electrode; a drive section for allowing the workpiece held
by the holder and the processing electrode, facing each other, to
make a relative movement; and a numerical controller for effecting
a numerical control of the drive section.
[0012] The electrolytic processing apparatus makes it possible to
compare the form of a workpiece before or during processing with an
intended form of the workpiece after processing and determine the
processing amount corresponding to the coordinate difference
between the two forms, input parametric data corresponding to the
processing amount to the numerical controller and, based on the
inputted data, effect a numerical control of the drive section that
allows the workpiece held by the holder and the processing
electrode, facing each other, to make a relative movement. The
electrolytic processing apparatus, carried out under such a
numerical control, can produce the intended form of processed
workpiece with high accuracy of form.
[0013] The power source may supply an electric current or a voltage
controlled at a constant value between the processing electrode and
the feeding electrode.
[0014] In electrolytic processing, the processing rate is constant
when the electric current following between a processing electrode
and a feeding electrode is controlled at a constant value. In this
case, the processing amount is determined by the product of the
electric current value and the processing time. Accordingly, in the
case where the electric current flowing between a processing
electrode and a feeding electrode is controlled at a constant
value, an intended form of processed workpiece can be obtained with
high accuracy of form only by numerically controlling the
processing time, i.e. a period of time during which the workpiece
and the processing electrode face each other, so that the
electrolytic processing phenomenon occurs (residence time).
[0015] The numerical controller may numerically control, for
example, the relative movement speed between the workpiece held by
the holder and the processing electrode via the drive section.
[0016] When carrying out electrolytic processing while allowing the
workpiece held by the holder and the processing electrode, facing
each other, to make a relative movement with changing relative
speeds, the changing relative movement speeds may be numerically
controlled. This makes it possible to process a certain point in
the processing surface of the workpiece for an optimum processing
time (residence time).
[0017] Alternatively, the numerical controller may numerically
control a stop time in a relative step movement of the workpiece
held by the holder and the processing electrode via the drive
section.
[0018] When carrying out electrolytic processing while allowing the
workpiece held by the holder and the processing electrode, facing
each other, to make a relative step movement, the stop time in the
movement is numerically controlled. This makes it possible to
process a certain point in the processing surface of the workpiece
for an optimum processing time (residence time).
[0019] The term "relative step movement" herein refers to such a
relative movement that either one or both of the workpiece and the
processing electrode move so that the processing electrode makes a
repetition of a certain-distance movement and stop over the
workpiece.
[0020] The present invention provides an electrolytic processing
method, comprising: providing a processing electrode, a feeding
electrode and an ion exchanger disposed in at least one of the
space between a workpiece held by a holder and the processing
electrode and the space between the workpiece and the feeding
electrode; allowing the processing electrode to be close to or in
contact with the workpiece held by the holder while feeding
electricity from the feeding electrode to the workpiece; supplying
a fluid to the space between the workpiece and at least one of the
processing electrode and the feeding electrode, in which the ion
exchanger is present; applying a voltage between the processing
electrode and the feeding electrode; and allowing the workpiece
held by the holder and the processing electrode, facing each other,
to make a relative movement while numerically controlling the
movement by a numerical controller.
[0021] The electrolytic processing method may be comprising:
measuring the form of the workpiece before and/or during
processing; inputting coordinate data on the measured form and on
an intended form after processing of the workpiece to the numerical
controller; and numerically controlling the relative movement speed
between the workpiece held by the holder and the processing
electrode according to the coordinate difference between the
measured form and the intended form.
[0022] The electrolytic processing method may be comprising:
measuring the form of the workpiece before and/or during
processing; inputting coordinate data on the measured form and on
an intended form after processing of the workpiece to the numerical
controller; and numerically controlling a stop time in a relative
step movement of the workpiece held by the holder and the
processing electrode according to the coordinate difference between
the measured form and the intended form.
[0023] The above and other objects, features, and advantages of the
present invention will be apparent from the following description
when taken in conjunction with the accompanying drawings which
illustrates preferred embodiments of the present invention by way
of example.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a longitudinal sectional front view of an
electrolytic processing apparatus according to a first embodiment
of the present invention;
[0025] FIG. 2 is a diagram illustrating the relationship between
the pre-processing form and an intended post-processing form of a
workpiece;
[0026] FIG. 3 is a block diagram illustrating an example of
numerical control by the electrolytic processing apparatus of FIG.
1;
[0027] FIG. 4 is a longitudinal sectional front view of an
electrolytic processing apparatus according to a second embodiment
of the present invention;
[0028] FIG. 5 is a schematic perspective view of an electrolytic
processing apparatus according to a third embodiment of the present
invention;
[0029] FIG. 6 is a block diagram illustrating an example of
numerical control by the electrolytic processing apparatus of FIG.
5;
[0030] FIG. 7 is a schematic perspective view of an electrolytic
processing apparatus according to a fourth embodiment of the
present invention;
[0031] FIGS. 8A through 8C are diagrams illustrating, in sequence
of process steps, an example of the formation of copper
interconnects; and
[0032] FIG. 9 is a diagram illustrating the principle of
electrolytic processing as carried out by using an ion
exchanger.
BEST MODE FOR CARRYING OUT THE INVENTION
[0033] Preferred embodiments of the present invention will now be
described with reference to the drawings. Though the
below-described embodiments refer to application to electrolytic
processing apparatuses (electrolytic polishing apparatuses) which
use a substrate as a workpiece to be processed and remove (polish)
copper formed on the surface of the substrate, the present
invention is of course applicable to other workpiece, and to other
electrolytic processing.
[0034] FIG. 1 shows an electrolytic processing apparatus according
to a first embodiment of the present invention. This electrolytic
processing apparatus includes a substrate holder 30 for attracting
and holding the substrate W with its front surface facing upward
(so-called "face-up" manner) , and an electrode head 38 having a
disc-shaped electrode section 36 made of an insulating material.
The electrode section 36 has, embedded therein, fan-shaped
processing electrodes 32 and feeding electrodes 34 that are
disposed alternately with their surfaces (lower faces) exposed. The
electrode head 38 is positioned above the substrate holder 30. An
ion exchanger 40 consisting of laminated layers (lamination) is
mounted on the lower surface of the electrode section 36 so as to
cover the surfaces of the processing electrodes 32 and the feeding
electrodes 34.
[0035] The substrate holder 30 is connected directly to the upper
end of a supporting shaft 42 which is supported rotatably. A motor
44 as a first drive section for making the relative movement
between the substrate W held by the substrate holder 30 and the
processing electrodes 32 is disposed beside the supporting shaft
42. A timing belt 46 is engaged between the supporting shaft 42 and
the motor (first drive section) 44 so that the substrate holder 30
and the substrate W held by the substrate holder 30 rotate
integrally by the actuation of the motor (first drive section)
44.
[0036] The electrode head 38 is connected downwardly to the free
end of a pivot arm 48 which can pivot horizontally. The base
portion of the pivot arm 48 is connected to the upper end of a
hollow pivot shaft 54 which moves vertically via a ball screw 52 by
the actuation of a motor 50 for vertical movement. A motor 56, as a
second drive section for making the relative movement between the
substrate W held by the substrate holder 30 and the processing
electrodes 32, is positioned beside the pivot shaft 54, and allows
to move vertically with the pivot shaft 54. A timing belt 58 is
engaged between the pivot shaft 54 and the motor (second drive
section) 56 so that the pivot shaft 54 and the pivot arm 48 pivots
(rotates) integrally by the actuation of the motor (second drive
section) 56.
[0037] Further, the electrode head 38 is connected directly to a
hollow motor 60 as a third drive section for making the relative
movement between the substrate W held by the substrate holder 30
and the processing electrodes 32 so as to rotate by the actuation
of the hollow motor (third drive section) 60.
[0038] In this embodiment, the ion exchanger 40 is of a three-layer
structure (lamination) consisting of a pair of strongly acidic
cation-exchange fibers 62a, 62b and a strongly acidic
cation-exchange membrane 62c interposed between the fibers 62a,
62b. The ion exchanger (laminate) 40 has a good water permeability
and a high hardness and, in addition, the exposed surface (lower
surface) to be opposed to the substrate W has a good smoothness.
The construction of the ion exchanger 40 may be arranged such that
the ion-exchange membrane is used for the exposed surface and the
laminate of the ion-exchange fibers is arranged above the exposed
ion-exchange membrane.
[0039] Each of the laminated layers 62a, 62b and 62c of the ion
exchanger 40 preferably carries a strongly acidic cation-exchange
group (sulfonic acid group) , however, an ion exchanger carrying a
weakly acidic cation-exchange group (carboxyl group), an ion
exchanger carrying a strongly basic anion-exchange group
(quaternary ammonium group), or an ion exchanger carrying a weakly
basic anion-exchange group. (tertiary or lower amino group) may be
used.
[0040] The nonwoven fabric carrying a strongly basic anion-exchange
group can be prepared by, for example, the following method: A
polyolefin nonwoven fabric having a fiber diameter of 20-50 .mu.m
and a porosity of about 90% is subjected to the so-called radiation
graft polymerization, comprising .gamma.-ray irradiation onto the
nonwoven fabric and the subsequent graft polymerization, thereby
introducing graft chains; and the graft chains thus introduced are
then aminated to introduce quaternary ammonium groups there into.
The capacity of the ion-exchange groups introduced can be
determined by the amount of the graft chains introduced. The graft
polymerization may be conducted by the use of a monomer such as
acrylic acid, styrene, glicidyl methacrylate, sodium
styrenesulfonate or chloromethylstyrene. The amount of the graft
chains can be controlled by adjusting the monomer concentration,
the reaction temperature and the reaction time. Thus, the degree of
grafting, i.e. the ratio of the weight of the nonwoven fabric after
graft polymerization to the weight of the nonwoven fabric before
graft polymerization, can be made 500% at its maximum.
Consequently, the capacity of the ion-exchange groups introduced
after graft polymerization can be made 5 meq/g at its maximum.
[0041] The nonwoven fabric carrying a strongly acidic
cation-exchange group can be prepared by the following method: As
in the case of the nonwoven fabric carrying a strongly basic
anion-exchange group, a polyolefin nonwoven fabric having a fiber
diameter of 20-50 .mu.m and a porosity of about 90% is subjected to
the so-called radiation graft polymerization comprising .gamma.-ray
irradiation onto the nonwoven fabric and the subsequent graft
polymerization, thereby introducing graft chains; and the graft
chains thus introduced are then treated with a heated sulfuric acid
to introduce sulfonic acid groups there into. If the graft chains
are treated with a heated phosphoric acid, phosphate groups can be
introduced. The degree of grafting can reach 500% at its maximum,
and the capacity of the ion-exchange groups thus introduced after
graft polymerization can reach 5 meq/g at its maximum.
[0042] The base material of each of the laminated layers 62a, 62b
and 62c of the ion exchanger 40 may be a polyolefin such as
polyethylene or polypropylene, or any other organic polymer.
Further, besides the form of a nonwoven fabric, the ion exchanger
may be in the form of a woven fabric, a sheet, a porous material,
net or short fibers, etc.
[0043] When polyethylene or polypropylene is used as the base
material, graft polymerization can be effected by first irradiating
radioactive rays (.gamma.-rays or electron beam) onto the base
material (pre-irradiation) to thereby generate a radical, and then
reacting the radical with a monomer, whereby uniform graft chains
with few impurities can be obtained. When an organic polymer other
than polyolefin is used as the base material, on the other hand,
radical polymerization can be effected by impregnating the base
material with a monomer and irradiating radioactive rays
(.gamma.-rays, electron beam or UV-rays) onto the base material
(simultaneous irradiation). Though this method fails to provide
uniform graft chains, it is applicable to a wide variety of base
materials.
[0044] By using each of the laminated layers 62a, 62b and 62c of
the ion exchanger 40 made of a nonwoven fabric, which liquid can
flows therethrough, having an anion-exchange group or a
cation-exchange group, it becomes possible that the ion-exchange
reaction between ions in the liquid and the ion-exchange group of
the ion exchanger can be easily taken place.
[0045] When each of the laminated layers 62a, 62b and 62c of the
ion exchanger 40 has only one of anion-exchange group and
cation-exchange group, a limitation is imposed on electrolytically
processible materials and, in addition, impurities are likely to
form due to the polarity. In order to solve this problem, the anion
exchangers and the cation exchangers may be superimposed, or each
of the laminated layers 62a, 62b and 62c of the ion exchanger 40
may carry both of an anion-exchange group and a cation-exchange
group per se, whereby a range of materials to be processed can be
broadened and the formation of impurities can be restrained.
[0046] Further, by making the ion exchanger 40 a multi-layer
structure consisting of laminated layers of ion-exchange materials,
such as a nonwoven fabric, a woven fabric and a porous membrane, it
is possible to increase the total ion exchange capacity of the ion
exchanger 40, whereby formation of an oxide, for example, in
removal (polishing) processing of copper, can be restrained to
thereby avoid the oxide adversely affecting the processing rate. In
this regard, when the total ion exchange capacity of an ion
exchanger 40 is smaller than the amount of copper ions taken in the
ion exchanger 40 during removal processing, the oxide should
inevitably be formed on the surface or in the inside of the ion
exchanger 40, which adversely affects the processing rate. Thus,
the formation of the oxide is governed by the ion exchange capacity
of an ion exchanger, and copper ions exceeding the capacity should
become the oxide. The formation of an oxide can thus be effectively
restrained by using, as the ion exchanger, a multi-layer ion
exchanger composed of laminated layers of ion-exchange materials
which has enhanced total ion exchange capacity.
[0047] The ion exchanger 40 should preferably have water
permeability and water-absorbing properties. Further, it is
desirable that at least the material to be opposed to the workpiece
has a high hardness and good surface smoothness. For example, a
commercially-available foamed polyurethane "IC 1000" (manufactured
by Rodel, Inc.) , generally employed as a pad for CMP, is hard and
excellent in wear resistance. By providing a number of
through-holes, this product can be used as a material for each of
the laminated layers of the ion exchanger 40. It is possible to
provide holes in a resin plate, thereby making the plate
water-permeable for use in the ion exchanger 40. It is of course
desirable that the quality of the material has "water-absorbing
properties".
[0048] According to this embodiment, a plurality of fan-shaped
electrode plates 64 are disposed in the electrode section 36 in the
circumference direction, and the cathode and anode of a power
source 68 are alternately connected, via a slip ring 66, to the
electrode plates 64. The electrode plates 64 connected to the
cathode of the power source 68 become the processing electrodes 32
and the electrode plates 64 connected to the anode of the power
source 68 become the feeding electrodes 34. This applies to
processing of e.g. copper, because electrolytic processing of
copper proceeds on the cathode side.
[0049] Depending upon a material to be processed, the cathode side
can be a feeding electrode and the anode side can be a processing
electrode. More specifically, when the material to be processed is
copper, molybdenum, iron or the like, electrolytic processing
proceeds on the cathode side, and therefore the electrode plates 64
connected to the cathode of the power source 68 should be the
processing electrodes 32 and the electrode plates 64 connected to
the anode should be the feeding electrodes 34. In the case of
aluminum, silicon or the like, on the other hand, electrolytic
processing proceeds on the anode side. Accordingly, the electrode
plates connected to the anode of the power source should be the
processing electrodes and the electrode plates connected to the
cathode should be the feeding electrodes.
[0050] By thus disposing the processing electrodes 32 and the
feeding electrodes 34 separately and alternately in the
circumferential direction of the electrode section 36, fixed
feeding portions to supply electricity to a conductive film
(portion to be processed) of the substrate is not needed, and
processing can be effected to the entire surface of the substrate.
Further, be changing the positive and negative in a pulse manner or
alternately, an electrolysis product can be dissolved and the
flatness of the processed surface can be enhanced by the multiplex
repetition of processing.
[0051] With respect to the processing electrode 32 and the feeding
electrode 34, oxidation or dissolution thereof due to an
electrolytic reaction is generally a problem. In view of this, it
is preferred to use, as a base material of the feeding electrode
34, carbon, a noble metal that is relatively inactive, a conductive
oxide or a conductive ceramics, rather than a metal or metal
compound widely used for electrodes. A noble metal-based electrode
may, for example, be one obtained by plating or coating platinum or
iridium onto a titanium electrode, and then sintering the coated
electrode at a high temperature to stabilize and strengthen the
electrode. Ceramics products are generally obtained by
heat-treating inorganic raw materials, and ceramics products having
various properties are produced from various raw materials
including oxides, carbides and nitrides of metals and nonmetals.
Among them there are ceramics having an electric conductivity. When
an electrode is oxidized, the value of the electric resistance
generally increases to cause an increase of applied voltage.
However, by protecting the surface of an electrode with a
non-oxidative material such as platinum or with a conductive oxide
such as an iridium oxide, the decrease of electric conductivity due
to oxidation of the base material of an electrode can be
prevented.
[0052] A pure water nozzle 70 as a pure water supply section for
supplying pure water or ultrapure water toward the space between
the substrate W held by the substrate holder 30 and the lowered
electrode head 38 is disposed above the substrate holder 30. Pure
water or ultrapure water is thus supplied to the ion exchanger 40.
Pure water herein refers to a water having an electric conductivity
of not more than 10 .mu.S/cm, and ultrapure water refers to a water
having an electric conductivity of not more than 0.1 .mu.S/cm. The
electric conductivity of the present invention refers herein to
that at 25.degree. C., latm. Instead of pure water or ultrapure
water, a liquid having an electric conductivity of not more than
500 .mu.S/cm or any electrolytic solution may be used. By supplying
such a liquid during processing, the instability factors of
processing, such as process products and dissolved gases, can be
removed, and processing can be effected uniformly with good
reproducibility.
[0053] The electrolytic processing apparatus is provided with a
numerical controller 72 for effecting numerical control of the
drive sections, i.e. the motor (first drive section) 44, the motor
(second drive section) 56 and the motor (third drive section) 60,
which allow the substrate W held by the substrate holder 30 and the
processing electrodes 32, facing each other, to make a relative
movement. The motors (drive sections) 44, 56 and 60 are thus
numerically controllable servomotors, and their rotation angles and
rotational speeds are numerically controlled by an output signal
from the numerical controller 72.
[0054] According to this embodiment, during electrolytic processing
carried out while being flowed an electric current at a constant
value between the processing electrodes 32 and the feeding
electrodes 34, the numeral controller 72 numerically controls: the
rotational speed of the substrate W, held by the substrate holder
30, via the motor (first drive section) 44; the speed of the
horizontal movement of the electrode head 38, by pivoting of the
pivot arm 48, via the motor (second drive section) 56; and the
rotational speed of the electrode head 38 via the motor (third
drive section) 60.
[0055] An example of the numerical control will now be described
with reference to FIGS. 2 and 3. First, as shown in FIG. 2, the
form of a substrate (workpiece) before processing is measured.
Specifically, various coordinate points of the pre-processing form
are measured in a X-Y-Z coordinate system (in which the Z axis is
orthogonal to the X-Y plane as a datum plane). The measured
pre-processing form data is inputted to the numerical controller
72. Further, with respect to a coordinate point (x, y, Z.sub.1) of
the pre-processing form, the corresponding coordinate point (x, y,
Z.sub.2) of an intended post-processing form is also inputted as
intended form data to the numerical controller 72. In addition,
unit processing form data (movement speed per motor control signal
pulse) e.g. on form and on processing rate is inputted to the
numerical controller 72 in advance or at an arbitrary time.
[0056] When electrolytic processing is carried out under control of
the electric current flowing between the processing electrodes 32
and the feeding electrodes 34 at a constant value, the processing
rate is constant thereby the processing amount is determined by the
product of the current value and the processing time. Accordingly,
in the case where the electric current flowing between the
processing electrodes 32 and the feeding electrodes 34 is
controlled at a constant value, an intended form of processed
substrate can be obtained with high accuracy of form only by
numerically controlling the processing time, i.e. a period of time
during which the substrate W and the processing electrodes 32 face
each other, so that the electrolytic processing phenomenon occurs
(residence time).
[0057] Thus, according to this embodiment, a processing amount
Z.sub.1-Z.sub.2 in the Z direction is determined at each coordinate
point based on the data inputted in the numerical controller 72.
Based on the processing amount Z.sub.1-Z.sub.2, the rotational
speed of the substrate W, held by the substrate holder 30, via the
motor (first drive section) 44; the speed of the horizontal
movement of the electrode head 38, by pivoting of the pivot arm 48,
via the motor (second drive section) 56; and the rotational speed
of the electrode head 38 via the motor (third drive section) 60 are
determined for each coordinate point, and the signal is inputted to
the motors (drive sections) 44, 56 and 60 so as to numerically
control the motors (drive sections) 44, 56 and 60.
[0058] Next, electrolytic processing by this electrolytic
processing apparatus will be described.
[0059] First, a substrate W, e.g. a substrate W as shown in FIG. 8B
which has in its surface a copper film 6 as a conductor film
(portion to be processed), is attracted and held by the substrate
holder 30, and the electrode head 38 is moved by the pivot arm 48
to a processing position right above the substrate W held by the
substrate holder 30. The electrode head 38 is then lowered by the
actuation of the motor 50 for vertical movement, so that the ion
exchanger 40 mounted on the lower surface of the electrode section
36 of the electrode head 38 contacts or gets close to the upper
surface of the substrate W held by the substrate holder 30.
[0060] Next, an electric power is applied from the power source 68
to between the processing electrodes 32 and the feeding electrodes
34, while the electric current flowing between the processing
electrodes 32 and the feeding electrodes 34 being controlled at a
constant value, and the substrate holder 30 and the electrode head
38 are rotated. Further, the pivot arm 48 is pivoted to move the
electrode head 38 horizontally. At the same time, pure water or
ultrapure water is supplied from the pure water nozzle 70 disposed
above the electrode substrate holder 30 to between the substrate W
and the electrode head 38, thereby filling pure water or ultrapure
water into the space between the processing and feeding electrodes
32, 34 and the substrate W. Thereby, electrolytic processing of the
conductor film (copper film 6) formed on the substrate W is
effected by hydrogen ions or hydroxide ions produced in the ion
exchanger 40.
[0061] More specifically, pure water or ultrapure water is
dissociated into OH.sup.- ions and H.sup.+ ions with the aid of a
catalytic reaction in the ion exchanger 40. The OH.sup.- ions
transfer the electric charges in the vicinity of the processing
electrodes 32 and become OH radicals. The OH radicals are reacted
with the copper film 6 of the substrate W to thereby effect removal
(polishing) processing of the copper film 6. In order to shut off
H.sub.2 gas generated at the feeding electrodes 34, a
gas-impermeable ion membrane may be used as the strongly acidic
cation-exchange membrane 62. The H.sub.2 gas is thus shut off, and
is discharged out by the flow of pure water or ultrapure water
produced by the rotation of the electrode section 36.
[0062] More specifically, by allowing pure water or ultrapure water
to flow within the ion exchanger 40, a sufficient amount of water
can be supplied to a functional group (sulfonic acid group in the
case of an ion exchanger carrying a strongly acidic cation-exchange
group) thereby to increase the amount of dissociated water
molecules, and the process product (including a gas) formed by the
reaction between the conductor film (copper film 6) and hydroxide
ions (or OH radicals) can be removed by the flow of water, whereby
the processing efficiency can be enhanced. The flow of pure water
or ultrapure water is thus necessary, and the flow of water should
desirably be constant and uniform. The constancy and uniformity of
the flow of water leads to constancy and uniformity in the supply
of ions and the removal of the process product, which in turn leads
to constancy and uniformity in the processing.
[0063] By making the ion exchanger 40 of a laminate of a
multi-layer structure, the total ion-exchange capacity of the ion
exchanger (laminate) 40 can be increased, whereby the reaction
products (oxides and ions) of the electrolytic reaction can be
prevented from accumulating in the ion exchanger 40 in an amount
exceeding the accumulation capacity of the laminate. In this
regard, if the reaction products are accumulated in the laminate in
an amount exceeding the accumulation capacity, the accumulated
products may change their forms, and such transformed products can
adversely affect the processing rate and its distribution.
Moreover, the flatness of the processed surface of the substrate
can be enhanced by using, as the ion exchanger 40, one having a
high hardness or one having a good surface smoothing, or by using
both of them.
[0064] In advance, the pre-processing form data, intended form data
and the unit processing form data are inputted to the numerical.
controller 72. Electrolytic processing is carried out while
numerically controlling: the rotational speed of the substrate w,
held by the substrate holder 30, via the motor (first drive
section) 44; the speed of the horizontal movement of the electrode
head 38, by pivoting of the pivot arm 48, via the motor (second
drive section) 56; and the rotational speed of the electrode head
38 via the motor (third drive section) 60.
[0065] In the electrolytic processing, the electric current flowing
between the processing electrodes 32 and the feeding electrodes 34
is controlled at a constant value to thereby fix the processing
rate while the relative movement between the substrate W and the
processing electrodes 32 being numerically controlled. The
electrolytic processing can produce an intended form of processed
substrate (workpiece) W with high accuracy of form.
[0066] After completion of the electrolytic processing, the power
source 68 is disconnected, the rotation of the substrate holder 30
and the electrode head 38 are stopped, and pivoting of the pivot
arm 48 is stopped. Thereafter, the electrode head 38 is raised, and
processed substrate W held by the substrate holder 30 is
transferred to next process.
[0067] This embodiment shows the case of supplying pure water,
preferably ultrapure water, to the space between the electrode
section 36 and the substrate W. The use of pure water or ultrapure
water containing no electrolyte upon electrolytic processing can
prevent extra impurities such as an electrolyte from adhering to
and remaining on the surface of the substrate w. Further, copper
ions or the like dissolved during electrolytic processing are
immediately caught by the ion exchanger 40 through the ion-exchange
reaction. This can prevent the dissolved copper ions or the like
from re-precipitating on the other portions of the substrate W, or
from being oxidized to become fine particles which contaminate the
surface of the substrate W.
[0068] Ultrapure water has a high resistivity, and therefore an
electric current is hard to flow therethrough. A lowering of the
electric resistance is made by shortening a distance between the
electrode and the workpiece, or interposing the ion exchanger
between the electrode and the workpiece. Further, an electrolytic
solution, when used in combination with electrolytic solutions, can
further lower the electric resistance and reduce the power
consumption. When electrolytic processing is conducted by using an
electrolytic solution, the portion of a workpiece that undergoes
processing ranges over a slightly wider area than the area of the
processing electrode. In the case of the combined use of ultrapure
water and the ion exchanger, on the other hand, since almost no
electric current flows through ultrapure water, electric processing
is effected only within the area of a workpiece that is equal to
the area of the processing electrode and the ion exchanger.
[0069] It is possible to use, instead of pure water or ultrapure
water, an electrolytic solution obtained by adding an electrolyte
to pure water or ultrapure water. The use of such an electrolytic
solution can further lower the electric resistance and reduce the
power consumption. A solution of a neutral salt such as NaCl or
Na.sub.2SO.sub.4, a solution of an acid such as HCl or
H.sub.2SO.sub.4, or a solution of an alkali such as ammonia, may be
used as the electrolytic solution, and these solutions may be
selectively used according to the properties of the workpiece. When
the electrolytic solution is used, it is preferred to provide a
slight interspace between the substrate W and the ion exchanger 40
so that they are not in contact with each other.
[0070] Further, it is also possible to use, instead of pure water
or ultrapure water, a liquid obtained by adding a surfactant or the
like to pure water or ultrapure water, and having an electric
conductivity of not more than 500 .mu.S/cm, preferably not more
than 50 S/cm, more preferably not more than 0.1 .mu.S/cm
(resistivity of not less than 10 M.OMEGA..multidot.cm). Due to the
presence of a surfactant in pure water or ultrapure water, the
liquid can form a layer, which functions to inhibit ion migration
evenly, at the interface between the substrate W and the ion
exchanger 40, thereby moderating concentration of ion exchange
(metal dissolution) to enhance the flatness of the processed
surface. The surfactant concentration is desirably not more than
100 ppm. When the value of the electric conductivity is too high,
the current efficiency is lowered and the processing rate is
decreased. The use of the liquid having an electric conductivity of
not more than 500 .mu.S/cm, preferably not more than 50 .mu.S/cm,
more preferably not more than 0.1 .mu.S/cm, can attain a desired
processing rate.
[0071] According to the embodiment, the processing rate can be
considerably enhanced by interposing the ion exchanger 40 between
the substrate W and the processing and feeding electrodes 32, 34.
In this regard, electrochemical processing using ultrapure water is
effected by a chemical interaction between hydroxide ions in
ultrapure water and a material to be processed. However, the amount
of the hydroxide ions acting as reactant in ultrapure water is as
small as 10.sub.-7 mol/L under normal temperature and pressure
conditions, so that the removal processing efficiency can decrease
due to reactions (such as an oxide film-forming reaction) other
than the reaction for removal processing. It is therefore necessary
to increase hydroxide ions in order to conduct removal processing
efficiently. A method for increasing hydroxide ions is to promote
the dissociation reaction of ultrapure water by using a catalytic
material, and an ion exchanger can be effectively used as such a
catalytic material. More specifically, the activation energy
relating to water-molecule dissociation reaction is lowered by the
interaction between functional groups in an ion exchanger and water
molecules, whereby the dissociation of water is promoted to thereby
enhance the processing rate.
[0072] Further, according to this embodiment, the ion exchanger 40
is brought into contact with or close to the substrate W upon
electrolytic processing. When the ion exchanger 40 is positioned
close to the substrate W, though depending on the distance
therebetween, the electric resistance is large to some degree and,
therefore, a somewhat large voltage is necessary to provide a
requisite electric current density. However, on the other hand,
because of the non-contact relation, it is easy to form flow of
pure water or ultrapure water along the surface of the substrate W,
whereby the reaction product produced on the substrate surface can
be efficiently removed. In the case where the ion exchanger 40 is
brought into contact with the substrate W, the electric resistance
becomes very small and therefore only a small voltage needs to be
applied, whereby the power consumption can be reduced.
[0073] If a voltage is raised to increase the current density in
order to enhance the processing rate, an electric discharge can
occur when the electric resistance between the electrode and the
substrate (workpiece to be processed) is large. The occurrence of
electric discharge causes etch pits on the surface of the
workpiece, thus failing to form an even and flat processed surface.
To the contrary, since the electric resistance is very small when
the ion exchanger 40 is in contact with the substrate W, the
occurrence of an electric discharge can be avoided.
[0074] FIG. 4 shows an electrolytic processing apparatus according
to a second embodiment of the present invention. The electrolytic
processing apparatus has a ring-shaped contact holding plate 80 at
the periphery of the upper surface of the substrate holder 30. A
plurality of inwardly-protruding contacts 82 as feeding electrodes
are mounted at a given pitch to the contact holding plate 80.
Further, the electrode head 38 is provided with a processing
electrode 84 instead of the electrode section 36 used in the
embodiment of FIG. 1. The processing electrode 84 is connected to
the cathode of the power source 68 via a slip ring 86, and the
contacts (feeding electrodes) 82 are connected to the anode of the
power source 68. The other construction is the same as the
apparatus shown in FIG. 1.
[0075] According to this embodiment, when a substrate W is held by
the substrate holder 30, the contacts (feeding electrodes) 82
contact the copper layer 6 as a to-be-processed material, deposited
on the surface of the substrate W as shown in FIG. 8B. Electrolytic
processing can be carried in the same manner as in the preceding
embodiment Thus, the electrode head 38 is lowered, and a electric
current is applied from the power source 68 to between the
processing electrode 84 and the contacts (feeding electrodes) 82 at
a constant value while the substrate holder 30 and the electrode
head 38 being rotated, and the pivot arm 48 being pivoted to move
the electrode head 38 horizontally. At the same time, pure water or
ultrapure water is supplied from the pure water nozzle 70 to
between the substrate W and the processing electrode 84.
Electrolytic processing of the conductive film (copper film 6) of
the substrate W is thus effected.
[0076] In advance of the electrolytic processing, as with the
processing embodiment described above, the pre-processing form
data, the intended form data, the unit processing form data are
inputted to the numerical controller 72 so as to numerically
control: the rotational speed of the substrate W, held by the
substrate holder 30, via the motor (first drive section) 44; the
speed of the horizontal movement of the electrode head 38, by
pivoting of the pivot arm 48, via the motor (second drive section)
56; and the rotational speed of the electrode head 38 via the motor
(third drive section) 60. The electrolytic processing carried out
under such a control can produce an intended form of processed
substrate W with high accuracy of form.
[0077] FIG. 5 shows an electrolytic processing apparatus according
to a third embodiment of the present invention. The electrolytic
processing apparatus includes a substrate holder 100 for attracting
and holding a substrate W with its front surface facing upward, and
a columnar or cylindrical processing electrode 102 disposed above
the substrate holder 100. The processing electrode 102 is coupled
to the free end of a horizontally-extending rotating shaft 104 that
is rotatable and vertically movable. An ion exchanger 106 is
mounted tightly on the outer circumferential surface of the
processing electrode 102. The substrate holder 100 and the
processing electrode 102 are disposed in a processing bath (not
shown) filled with a fluid, such as ultrapure water or pure water,
that is, they are immersed in the fluid.
[0078] The substrate holder 100 is coupled to the upper surface of
a rotating body 108 that rotates about a Z axis in the direction of
.theta.. The rotating body 108 is mounted on the upper surface of
an X-Y table 118 which includes an X stage 112 that moves in the X
direction by the actuation of a motor 110 as a first drive section
for allowing the substrate W, held by the substrate holder 100, and
the processing electrode 102 to make a relative movement in the X
direction, and a Y stage 116 that moves in the Y direction by the
actuation of a motor 114 as a second drive section for allowing the
substrate W, held by the substrate holder 100, and the processing
electrode 102 to make a relative movement in the Y direction.
[0079] A wire extending from the cathode of a power source 120 is
connected to the processing electrode 102, and a wire extending
from the anode is connected to a feeding electrode 122 that is
connected to an electric conductor, e.g. copper film 6 formed in
the substrate W as shown in FIG. 8B, and feeds electricity to the
conductor.
[0080] The processing bath is provided with a fluid nozzle as a
fluid supply section for supplying a fluid, such as pure water or
ultrapure water, into the processing bath.
[0081] The electrolytic processing apparatus is provided with a
numerical controller 124 for effecting a numerical control of the
drive sections, i.e. the motor 110 (first drive section) and the
motor 114 (second drive section), which allow the substrate W, held
by the substrate holder 100, and the processing electrode 102,
facing each other, to make a relative movement. The motors (drive
sections) 110, 114 are thus numerically controllable servomotors,
and their rotation angles and rotational speeds are numerically
controlled by an output signal from the numerical controller
124.
[0082] An example of the numerical control will now be described
with reference to FIG. 6. First, as illustrated in FIG. 2, the form
of the substrate (workpiece) before processing is measured by
measuring various coordinate points of the pre-processing form in
an X-Y-Z coordinate system (in which the Z axis is orthogonal to
the X-Y plane as a datum plane). The measured pre-processing form
data is inputted to the numerical controller 124. Further, with
respect to a coordinate point (x, y, Z.sub.1) of the pre-processing
form, the corresponding coordinate point (x, Y, Z.sub.2) of an
intended post-processing form is also inputted to the numerical
controller 124. In addition, unit processing form date (movement
speed per motor control signal pulse) e.g. on form and on
processing rate is inputted to the numerical controller 124 in
advance or at an arbitrary time.
[0083] According to this embodiment, a processing amount
Z.sub.1-Z.sub.2 in the Z direction is determined at each coordinate
point based on the data inputted in the numerical controller 124.
Based on the processing amount Z.sub.1-Z.sub.2, a period of time
during which the substrate W held by the substrate holder 100 is
stopped via the motor (first drive section) 110 and the motor
(second drive section) 114, is determined, and the signal is
inputted to the motors (drive sections) 110, 114 so as to
numerically control the motors 110, 114.
[0084] According to this embodiment, e.g. a substrate W as shown in
FIG. 8B, having copper film 6 as a conductive film (to-be-processed
portion)in the surface, is attracted and held by the substrate
holder 100. The ion exchanger 106 mounted on the surface of the
processing electrode 102 is brought close to or into contact with
the surface (upper surface) of the substrate W. Electrolytic
processing is then carried out by supplying an electric current
from the power source 120 to between the processing electrode 102
and the feeding electrode 122 at a constant value while rotating
the processing electrode 102.
[0085] During the electrolytic processing, a step movement, i.e. a
repetition of a movement and stop of the substrate W in the X or Y
direction, is carried out by the X-Y table 118. For this operation,
as described above, the pre-processing form date, the intended form
data and the unit processing form data are inputted to the
numerical controller 124 in advance, thereby numerically
controlling the stop time of the substrate W held by the substrate
holder 100 via the motor (first drive section) 110 and the motor
(second drive section) 114. The electrolytic processing performed
with such a controlled relative step movement can produce the
intended form of processed substrate with high accuracy of
form.
[0086] The term "relative step movement" herein refers to such a
relative movement that either one or both of the substrate W and
the processing electrode 102 move so that the processing electrode
102 makes a repetition of a certain distance-movement and stop over
the substrate W.
[0087] FIG. 7 shows an electrolytic processing apparatus according
to a fourth embodiment of the present invention. This embodiment
differs from the third embodiment shown in FIG. 5 in the use of a
spherical or oval processing electrode 102a.
[0088] When the processing electrode 102a is lowered, an ion
exchanger 106a, which is mounted on the surface of the processing
electrode 102a, is brought into point contact with the substrate W.
The processing electrode 102a is allowed to rotate while the ion
exchanger is in such contact with the substrate W. The other
construction is the same as the third embodiment.
[0089] According to this embodiment, the area of a portion (point)
under processing is small, whereby supply of ultrapure water or
pure water to around the processing portion can be made with ease,
enabling a stable processing.
[0090] According to the above-described embodiments, the drive
sections, which allow the substrate held by the substrate holder
and the processing electrode to make a relative movement, are
numerically controlled while the electric current flowing between
the processing electrode and the feeding electrode is controlled at
a constant value. It is, however, also possible to control the
voltage applied between the processing electrode and the feeding
electrode at a constant value, determine the electric current
flowing between the processing electrode and the feeding electrode
from the relationship between the voltage and electric current, and
numerically control the drive sections based on the electric
current thus determined.
[0091] The measurement of the form of a substrate (workpiece) may
be carried out not only before processing but also at any time
during processing any number of times. In this connection, there is
a case where the actual processing time becomes different from a
predetermined processing time. The difference can lead to a lowered
accuracy of form of the resulting processed substrate. Such a
lowering of accuracy may be eliminated or reduced by effecting
in-processing measurement of the substrate as many times as
possible. Thus, an increased number of in-processing measurements
can generally enhance the processing precision.
[0092] As described hereinabove, the present invention makes it
possible to compare the form of a workpiece before or during
processing with an intended form of the workpiece after processing
and determine the processing amount corresponding to the coordinate
difference between the two forms, input parametric data
corresponding to the processing amount to the numerical controller
and, based on the inputted data, effect numerical control of the
drive section that allows the workpiece held by the holder and the
processing electrode, facing each other, to make a relative
movement. The electrolytic processing, carried out under such a
numerical control, can produce the intended form of processed
workpiece with high accuracy of form.
[0093] Although certain preferred embodiments of the present
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
therein without departing from the scope of the appended
claims.
Industrial Applicability
[0094] This invention relates to an electrolytic processing
apparatus and method useful for processing a conductive material
present in the surface of a substrate, such as a semiconductor
wafer, or for removing impurities adhering to the surface of a
substrate.
* * * * *